A development device for the electrostatic photography, which comprises electroconductive electrode rollers operating as development electrodes respectively disposed movably upwardly and downwardly on a plurality of driving rollers arranged on a nearly horizontal level, and endless belt protruding from...http://www.google.fr/patents/US3774574?utm_source=gb-gplus-shareBrevet US3774574 - Development device for electrophotography

A development device for the electrostatic photography, which comprises electroconductive electrode rollers operating as development electrodes respectively disposed movably upwardly and downwardly on a plurality of driving rollers arranged on a nearly horizontal level, and endless belt protruding from the roller surfaces and mounted on both ends of the electrode rollers so as to carry electrophotographic material held between the endless belt and driving rollers, wherein plates are provided to shield a space between the electrode rollers in contact and adjacent to the endless belt, and comprising means for supplying a liquid developer over the electrode rollers.

[5 7] ABSTRACT A development device for the electrostatic photography, which comprises electroconductive electrode rollers operating as development electrodes respectively disposed-movably upwardly and downwardly on a plurality of driving rollers arranged on a nearly horizontal 1 level, and endless belt protruding from the roller surfaces and mounted on both ends of the electrode rollers so as to carry electrophotographic material held between the endless belt and driving rollers, wherein plates are provided to shield a space between the electrode rollers in contact andadjacent to the endless belt, and comprising means for supplying a liquid developer overthe electr ode rollers.

' 5 Claims, 4 Drawing Figures tive paper through one or more'sets of rollers, drive the rollers and supply developing liquid onto. the latent 7 4-4 in a vessel 1 containing a developing liquid 11. The

image on the surface of the paper while the rollers are being driven. During the driving, the rollers in contact with the surface bearing the latent'image serve as developing electrodes. I I

In accordance with one known device for the liquid development of electrophotogr'aphic' materials using rollers, the so called edging effect was avoided, i.e. it was not experienced that only the edge portion was developed and the middle portion of the paper was undeveloped. However, such a device has had a drawback. When the developingliquid is supplied onto the electrophotographic paper, it is likely to be supplied directly or through electrode rollers onto the surface of the paper. Accordingly, anynon-uniformity of supply of the developing liquid causes irregular development directly on the image. The developing liquid supplied I flows over the electrophotographic, paper to drop through the space between the side edge of the paper and the side plate of the rollers into a vessel 'atthe lowerpart of the development apparatus.

This flow of developing liquid results in a flow of developing liquid from the middle portion of the photosensitive paper ,to the edge of the paper, resulting in streaks on the image. I

SUMMARY- OF THE INVENTION I The invention provides a liquid developing device which can eliminate the above described disadvantage by means of developing liquid temporarily held nearly at rest on the photosensitive film in the course of development. An excellent image can be obtained having no developing irregularities without flow streaks due to the development liquid. v

The device according to the invention will be'described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION A PREFERRED EMBODIMENT FIGS. 1 and 2 illustrate an embodiment of the invention. Two side plates 2 (only one side plateis shown in FIG.'2 of the drawing) are provided which hold plural sets of rollers 3-1 and 4-1, 3-2 and 4-2, 3-4 and side plate 2 can be a metal or plastic plate having vertical grooves 5-1, 5-2, 5-4 holding an upper rollers 3-1, 3-4 (hereafterjcalled the electrode rollers) acting as developing electrodes, andthe other rollers 4-1, 4-4; of the roller sets can be driving rollers. Grooves 5-1, 5-4 are provided topermit electrode rollers 3-1, 3-4 to move upwardly and downwardly. The driving rollers 4-1,". 4-4 rotate in the direction of the arrow (driving rollers rotate at an equal speed through a driving means not shown). Driving roller 4-1, 4-4 can be made of metal or an alloy such asstainless steel, aluminum or 'brass, for example, with an outer diameter of 18 mm and a length of 200 mm. Electrode rollers 3-1, 3-4 can have the same dimensions and be of the same material as driving rollers 4-1, 4-4. In case of rollers 3-1, 3-4, the-diameter at I bothend. portions 7 is 0.1 to 1 mm smaller than the outer diameter. The length of the smaller diameter is 5 to 20 mm.

At both end portions 7 of rollers 3-1,,. 3-4 there are mounted an endless belts 8 which is electroconductive or insulating and of a flexible character. Rollers 3-l and 3-4 at their outermost edges (as shown in FIG. 1)

serveas support rollersfor the belt 8. By friction transmit the rotation of the driving rollers to the electrode rollers 3-1, 3-4 which is thereby rotated. This endless belt 8, has a widthof 5 to 20 mm and protrudes 0.05 2 mm from the outer diameter of the electrode roller 3 in such manner that it depends on the end portions 7 of the rollers 3-1, 3-4. Thus, the endless belt acts as spacer. Preferably, endless belt 8 is made of a plastic material such .as polytetrafluoroethylene (Trade name of Du Pont: Telflon), polyethylene, polyvinyl chloride,.and polyester, etc. Endless belt 8 rotates in close contact with side plate 2. Leakage of develop-- ing liquid from the space betweenthe belt 8 and the side plate 2 is, thus'prevented. Above the inner electrode rollers 3-2 and 3-3, there are provided developing I liquid feed-pipes 9-1, 9-2 carried by a support member (not shown). The developing liquid 11 contained in the vessel 1 is suctioned up by a pump (not shown) into feed pipes 9-1 and 9-2. The liquid is then supplied from aslit in pipes 9-1 and 9-2 onto inner'electrode rollers upwardly so that theendless belt 8 contacts both sides of the paper 12. The electrophotographic paper 12 will p I push up theelectrode rollers 3-1 the thickness of the photosensitive paper 12. Being compressed at both .ends by the belt 8, the paper advances at the peripheral speed of the'driving rollers 44. When the forward endof the electrophotographic paper 12 is caught by roller I set 3-2 and 4-2, the developing liquid which has been supplied from the slit 10-1 of the pipe 9-1 and dropping along the rotary direction of the roller 3-2 into the vessel l is accumulated in pool. The pool. is enclosed by I the paper 12 and the endless belt '8 as the bottom and the side plate 2 and rollers 3-1 and 3-2 as walls. The developing liquid will usually leak outward partly from between the endless belt 8 and the side plate 2 and electrostatic latent image formed on the surface of the electrophotographic paper with rollers 3-1 and 3-2 serving as development electrodes.

Similarly, as the electrophotographic paper 12 advances, a pool of developing liquid is formed, respectively, between the roller 3-2 and roller 3-3 and .be-

tween the roller 3-3 and roller3-4 to effect the development of the electrostatic latent image. Upon the further advance of the paper 12 and the separation of the rear end of the paper from the set of the rollers 3-1 and 4-1, the enclosure formed by the bottom of sensitive paper opens, and thedeveloping liquid pool accumulated between rollers 3-1 and 3-2 drops into the vessel 1. v

As the electrophotographic paper 12 advances, the developing liquid stored between rollers 3-2 and 3-3 I and between rollers 3-3 and 3-4 will thus be consecutively delivered into the vessel 1. 1

The obtained latent image has a very good continuous gradient without development irregularities.

The embodiment of the invention as hereinabove described provides a device for positive-positive development in which the toner adheres to the area of electrostatic charge. The device can also be used for reversal development, if the driving roller 4 and side plate 2 are insulated by bearings 6 and the electrode roller 3 and driving roller 4 have applied thereto a bias voltage.

FIG. 3 is a plan view of an essential portion of another practical embodiment of the invention. The embodiment provides the side plate 2 merely for holding the rollers. This embodiment of the invention features the provision of a liquid flow preventing plate 16 (as shown in FIG. 4) between the upper rollers shown in FIG. 3. In this manner, the dimensional accuracy required for the space between side plate 2 and the electrode roller 3 is lessened. As will be seen in FIG. '3, upper rollers 3-1 and 3-2 held in side plate 2 are provided with grooves 14 at slightly inward of their ends, the diameter of each of the grooves 14- being 0.1 1 mm smaller than the outer diameter of the rollers. Flexibleendless belt 8 is mounted on the rollers 3-1 and 3-2 in engagement with the groove 14 so as to operate as a spacer between the surface of the latent image and the electrode rollers. On the outside of groove 14'there A is provided a groove 15 for holding the liquid flow preventing plate 16.

The diameter of groove 15 is smaller than the outer diameter of roller 3 by more than 1 mm and its width is slightly more than the plate 16. The liquid preventing plate 16 is a flexible thin sheet made of metal or a plastic having a shape as shown in FIG. 4 and a thickness of 10 to 500 u. The liquid preventing plate 16 is held mounted by inserting its curved edges to thegroove 15 for shielding the side space between the rollers 3-1 and 3-2. The lower. side surfaces near the linear edges of the liquid flow preventing plate 16 slidably contact the outer edge sides of the endless belt.

The other portions of the device have the same shape and dimensions and are of the same materials as in the device of FIGS. 1 and 2.

Similar to the preceding embodiments, the photosensitive paper, upper rollers, and liquid preventing liquid form a pool subject to only slow leakage. The developing liquid is stored in the recess formed by the rollers 4 3-1 and 3-2, the liquid preventing plates ,16, the endless belts 8, and the electrophotographic paper. An excellent latent image was obtained using this combination.

The similar embodiment as shown in FIG. 3, which has liquid flow preventing plates 16 provided at the inner edge sides of endless belt 8, was capable of providing an image of excellent quality. The liquid flow preventing plate 16 may be provided in contact with the upper surface of the lower endless belt.

In accordance with this invention, the space between the endless belt, side plate, and liquid preventing flow plate has been almost eliminated. Freedom from criticality of the dimensions of the photosensitive paper andthis device were greatly increased. No significant flow of developing liquid occurred during development, so that the obtained image did not have flow or development irregularities.

While in the embodiment of FIG. 1 four sets of rollers were used, it will be clear that this is not a critical feature of the invention so long as the pool releasing feature is maintained. 7

Numerous modifications of the invention will become apparent to one of ordinary skill in the art upon reading the foregoing disclosure. During such a reading it will be evident that this invention provides a unique development device for electrophotography for accomplishing the objects and advantages herein stated.

We claim: l 1

1. A development device for the electrostatic photography, which comprises electroconductive electrode rollers operating as development electrodes respectively disposed above a plurality of driving rollers arranged on a nearly horizontal level, an endless belt protruding from the roller surfaces and mounted on both ends of said electrode rollers forconveying electrophotographic material held between said endless belt and driving rollers, provided to shield a space between the electrostatic material.

2. A development device as'in-claim 1 including means for positioning said electrode rollers upwardly and downwardly. l q

3. A development device as in claim 1 wherein the ends of said electrode rollers and said driving rollers are joumalled in said plate. A I I 4. A development device as in claim-l including a further plate in which the ends of said electrode rollers and said driving rollers are joumalled, said firstmentioned plate being supportedby said electrode rollers. v

5. A development device as in claim 4 wherein said first-mentioned plate is disposed in grooves at the ends of said electrode rollers and so shaped as to be supported by electrode rollers.